Yarn crimping apparatus and methods



June 13, 1961 N. E. KLEIN 2,987,869

YARN CRIMPING APPARATUS AND METHODS Filed Dec. 3. 1957 INVENTOR. NORMANE. KLEIN Eva/$5M ATTORNEY 2,987,869 YARN CRIMPING APPARATUS AND METHODNorman E. Klein, Pendleton, S.C., assignor to Bearing Milliken ResearchCorporation, Oconee, S.C., a corporation of Delaware Filed Dec. 3, 1957,Ser. No. 700,518 13 Claims. (Cl. 57-34) This invention relates to novelmethods and apparatus for the production of torsionally stressedthermoplastic yarns which tend to kink and curl when in an untensionedcondition.

Torsionally stressed thermoplastic yarns which tend to kink or curl arewell known in the art and are widely employed because of their elasticnature for a variety of purposes. They can be prepared by any number ofwell known processes, but the process which is presently most widelyemployed consists of highly twisting an end of yarn, setting the twist,for example, by means of heat and thereafter untwisting the yarn. Thethus treated yarn forms into loops and curls, when in an untensionedcondition, in an effort to relieve the torsional stresses created by theheatsetting and twisting operations. The twisting and untwisting of theyarn in a process of this nature can be accomplished by the insertion ofa true twist followed by a down twisting operation or it can beaccomplished by applying a false twist to a section of a running lengthof yarn and heatsetting the twist before it is removed.

The false twist method of producing a torsionally stressed yarn has theadvantage that the yarn need be handled a fewer number of times and theadvantage of a relatively high production rate, but has the disadvantageof requiring complicated apparatus not generally suitable for other usein the textile industry. Prior to this invention, the false twist methodhas generally required a rapidly rotating member, journaled at eitherend, which is provided with a central yarn passage for the yarn andmeans within the passage to force the yarn to rotate with the rotatingmember. One of these rotating members has been required for each strandof yarn being processed and, of course, there is also required a systemof pulleys, belts or the like for driving each of the rotating members.Even though the method is faster than the true twist procedure, it willbe apparent to those skilled in the art that the speed of rotation of amember such as described above must be relatively slow and this meansthat a large number of units and a considerable expenditure of powerwill be'necessary for the production of yarn in quantity. i

It is an object of this invention to provide novel methods and apparatusfor the production of torsionally stressed yarns which overcome thedisadvantages of prior art methods and apparatus.

It is another object of the invention to provide apparatus for theproduction of torsionally stressed yarns which apparatus is simple indesign, inexpensive to manufacture and economical to operate.

It is still another object of the'invention to provide apparatus forproducing crimped or curly yarn by the false twist procedure at a ratefar in excess of that heretofore possible.

It is a further object of the invention to provide a method forsimultaneously processing two strands of yarn wherein each of thestrands acts to insert false twist into the other.

The above as well as other objects of the invention are accomplished byan apparatus wherein two or more ends of'yarn under approximately equaltensions are wrapped several turns about each other and thereafterseparated and collected at substantially equal linear velocities. It hasbeen found that this single operation can result in 'nited States atenta high degree of false twist being inserted into each of the yarn ends,and if the yarn ends are heated while they are in a highly twistedcondition and are then allowed to cool or are cooled before they areuntwisted, an appreciable torsional stress is imparted in untwisting theyarns so that they subsequently assume a highly convoluted linearconfiguration when in a substantially tensionless condition.

The invention is operable with any thermoplastic yarn which is capableof having a twist heat-set therein. Typical examples of suitable yarnsare cellulose acetate, ny- =lon, polyester yarns such as that sold underthe trademark Dacron, and acrylic yarns such as those sold under thetrade-marks of 'Acrilan and Orlon. The invention is best employed withcontinuous filament yarns but if desired can frequently be employed toadvantage with spun yarns. It has also been found that best results areobtained with monofilamentary strands such as 15 denier monofilamentyarn but again the invention can also be employed with multifilamentarystrands. The invention can be employed with yarns of any total denierbut is preferably employed with smaller yarns, for example below aboutdenier. The maximum amount of twist that can normally be inserted by thenew method is approximately one turn of twist per VEJnD length of yarn,where D is the diameter of the yarn, and it will, therefore, be apparentthat if the diameter of the yarn is large, twist per unit length will below.

One preferred form of apparatus for performing the new method of theinvention will now be described with reference to the accompanyingdrawing which is a schematic view in perspective. The illustratedapparatus is suitable for simultaneously processing only two ends ofyarn but it will become apparent that the apparatus might be readilymodified to handle three or more ends.

With reference to the drawing in greater detail, there is illustrated apair of yarn supply packages 10 and 11, in each instance containing asupply of yarn. Yarn ends 12 and 13 are passed from the supply packages10 and 11 through a pair of pigtail guides 14 and 15, positioned axiallyof the yarn supply packages, which permits the yarn to be readilywithdrawn from the packages in an over-end manner.

Means are preferably provided for placing the yarn ends 12 and 13 undersubstantially equal tensions and in this instance is illustrated ascomprising a driven roll 17 about which each of the yarn ends 12 and 13may be wrapped one or more turns. The roll 17 is carried by a shaft 18which in turn is rotated by means of a sprocket 19 and a block chain 20.Chain 20 runs about a second sprocket 21 on a shaft 22 which in turn isdriven by an electrical motor 23 or by any other suitable source ofpower through a belt 24. Shaft 22 serves as a driving means for a pairof conventional yarn takeup devices in this instance illustrated ascomprising a pair of rolls '25 and 26 carried by the shaft 22 andengaging the yarn surfaces on a pair of takeup spools 27 and 28. As willbe apparent to those skilled in the art, this results in the yarn beingcollected at a uniform velocity regardless of the diameter of the yarnon the takeup package, and if the roll-s 25 and 26 are of the samediameter, yarn will be collected by spool 27 at substantially the samerate as by spool 23. A conventional transverse mechanism 29 isschematically illustrated and is for the purpose of winding the yarnevenly on the takeup packages.

The yarn ends from supply means 10 and 11 may be under very low tensionssince little resistance is met in removing the yarns in an over-endmanner, and to additionally tension the yarn ends to an extent that theydo not slip over the surface of roll 17, there is provided a pair ofpretensioning devices 40 and 41. The tensioning 3 devices 40 and 41 areillustrated as being of the disc type, but may be of any conventionaldesign or construction.

The illustrated arrangement, having a feed roll ar.

ranged for rotation ate constant rate with respect to the takeup rolls,is extremely advantageous for use with yarns, such as nylon, whichshrink an appreciable degree when heated. The speeds of rotation can be.such that the peripheral velocity of roll 17 is slightly, for example 1to in excess of the peripheral velocity of rolls and 26, since the yarnwill shrink to remove any slack that might otherwise result, and undersuch conditions it will be found that the tension in the yarn is acharacteristic of the specific yarn being employed and of thetemperature applied. In other words, the tension in a strand of nylonyarn being fed by roll 17 to spool 28 will be substantially identical tothe tension in a strand of nylon yarn being fed from roll 17 to spool 27if the temperature applied to both yarns is substantially equal and ifthe degree of overfeed is not in excess of about 10. With yarns that donot tend to shrink upon heating, an overfeed arrangement cannot beemployed and roll 17 must have .a peripheral velocity substantiallyequal to or slightly less than that of rolls 25 and 26. In fact, withyarns of this type it isgenerally advantageous to employ tensionregulating means of a more conventional type. Almost any conventionaltype of tension regulating device or even some types of simpletensioning devices can be employed since it is not necessary that theyarns be under identical tensions and the tensions in the strands mayoperatively difier as much as 10% or more. With some types of yarnsupply means it is even possible to dispense with supplementarytensioning means entirely since the supply means will deliver the yarnensd under tensions which sufficiently approximate each other to giveoperative results. It is, however, generally advantageous to employsupplemental tension regulating means so that the two yarn ends areunder as nearly the same tensions as possible since otherwise, when thetwo ends are twisted together, the end having the higher tension willserve more or less as a core for the end under a lower tension. This notonly lessens the degree of frictional contact to an extent that maypermit an objectionable degree of slippage, but can also result in moretwist being inserted in one strand than in the other so that the twoyarns, after processing, do not have comparable activities.

Positioned between the roll 17 and the transverse member19 are four yarnguide idler pulleys 30, 31, 32 and 33 positioned with respect to eachother so as to form the corners of an elongated rectangle. These pulleysmay be supported in any suitable manner and are, therefore, indicatedonly schematically in the drawing. Positioned in substantially the sameplane as the pulleys to 33 is a plate member 34- preferably made of aheat conducting metal or the like and which has a polished upper facesuitable for slideably engaging a strand of yarn. The plate 34 isadapted to be cooled by means of a con duit 35 carried by its lower faceand through which may be circulated a cooling fluid or the like. Alsolying in substantially the same plane as pulleys 30 to 33 and positionedbetween pulleys 3t) and 31 and plate 34 is a second plate indicated bythe reference numeral 36. The plate 36 is also preferably made of metalor other heat conducting material and has a smooth upper face forslidably engaging a plurality of strands of yarn. The plate 36 isadapted to be heated by any suitable means such as by an electricalresistance unit carried on its lower face and supplied with power fromany suitable source, not illustrated, by means of conductors 37.

In operation, the yarn ends 12 and 13 are lead from supply packages 10and 11 through guides 14 and 15 to 'pretensioning means '40 and =41 andare thereafter passed one or more turns around feed roll 17. The twoends of yarnare then passed about guide pulleys 30 and 31 and twistedtogether for a plurality of turnsas indicated'be- 4 tween the referencenumerals 38 and 39. The two ends are then separated, passed about guidepulleys 32 and 33 and over the transverse means 29 to takeup spools 27and 28. Plates 3-6 and 34 are then brought to the desired temperaturesand motor 23 is-energized to result in the two strands of yarn beingdrawn through theapparatus and collected on rolls 27 and 2d.

The plying together of the two ends of yarn causes them, in effect, toroll over each other as they are moved through their respective linearpaths and this results in the yarn ends being individually twisted atthe point 33 and then being untwisted as they are separatedat the point39. In other words, the yarn ends are individually twisted between thepoint 39 and the pulleys-30 and 31, as well as being twisted about eachother between the pointsSS and 39. if plate 36 is at a sufiiciently hightemperature, the twist in the yarn'between pulleys 30 and 31 and point33 is heat-set therein so that the yarn normally tends to twist when ina relaxed conditon and since the yarn is cooled belowa heat-settingtemperature by the time it reaches the point 339., .removal of the twistat this point torsionally stresses both yarn ends. Therefore, the yarncollected onpackages 27 and 28 will tend .to kink, cur-l or loop when itis removed therefrom and relieved of tension even though it maybe in asubstantially untwisted condition.

In View of the above discussion, it will be apparent that the yarn ends.may be heated at any point in their linear paths where they are in ahighly twisted condition if sufficient time is allowed for coolingbefore the ends reach the point where they are separated. However, theillustrated arrangement, wherein the yarn are heatedwell in advance ofthe point of mutual contact, is preferred since this allows more timefor cooling than would be available if the yarns were, for example,heated at a point intermediate the points 38 and 39 and, in'addition,better contact of the yarn with the heater element-is obtained. it islikewise not generally advantageous to have a heater element or the likein contactwith the yarns at the exact point at which they are broughttogether, since this might interfere with the twistingof :the individualends.

The degree of twist inserted into the individual yarn ends depends uponthe number of turns per unit length with which the two ends are pliedtogether between the poins 38' and 39 and this in turn depends upon thediameter of the yarn ends, upon the angle between the yarn ends as theyare brought'together, the angle between the yarn ends as they separateand, to some extent, upon the tension employed. With yarn of a givendiameter, the most convenient means of increasing or decreasing thedegree of twist inserted in the individual ends comprises increasing ordecreasing the angles between the yarn ends at the point where they cometogether and/or separate. This can readily be accomplished in theembodiment illustrated by increasing or decreasing the number of turnswith which the ends are plied together or more satisfactorily byincreasing the distance between pulleys 30 and 31 and/or the distancebetween the pulleys 3'2 and 331. Generally, the distances between thetwo sets of pulleys should be adjusted so that the angles between thetwo ends as they approach and as they separate are, in each instance,between about 30 and but a very low degree of twist is desired, theangles may in each instance be as small as about 10, and ifa-very'highdegree of twist is desired, the angles maybe as large as or even in someinstances.

The number of turns that the yarn should be twisted together between thepoints 38 and 39 .is not critical, but should be at least a sufiicientnumber of turns toelimimate, to a large extent, slippage between the twoends of yarn. Twisting the yarns together for two turns will generallygive operative results if the; yarns are under a relatively hightension, for-example l to 2Igms. per denier, but :as a general 111181116yarn should be twisted together for at least aboutlO to 15 :ormoreturns. There is no upper limit as to the number of turns-that may bemployed in twisting the two yarn ends together, but as a general rulethere is no advantage in twisting the two yarns together more than about20 to 30 turns.

The minimum tension under which the yarns should be placed depends uponthe size of the yarn and the number of turns which the yarns are twistedtogether. The yarns should be under sufiicient tension to insureadequate frictional contact between each other and to prevent kinking ofthe yarns at the point where they are highly twisted and yet the tensionshould not be so high as to stretch the yarns. As a general rule it canbe said that operative limits run from about 0.01 gm. per denier toabout 1 to 4 gms. per denier with the preferred range being from about0.05 to 0.6 gms. per denier.

The temperature of the plate 36 necessary for adequate heat-setting ofthe yarns is a function of the type and size of the yarns beingprocessed, of the width of the strip, and of the linear velocity of theyarn. Of course, the important consideration is that the yarn reach aproper heat-setting temperature and, as is well known, various types ofyarns require difierent temperatures for a reasonable degree ofheat-setting to be efiected. With nylon yarns, it is generallypreferable to make certain that the yarns reach a temperature of atleast about 160 F. and preferably a temperature of about 240 F. orhigher. On the other hand, the yarns should not be heated above theirsticking temperature since if heated above this temperature they tend tostick to the heating plate. The sticking temperature for nylon is about450 F. so that this is an operative upper limit for nylon yarns and as ageneral rule, it is not advantageous to heat nylon yarns above about 380F. Inasmuch as heat-setting of yarns is such a common practice and is aprocedure familiar to those skilled in the art, a proper temperature forother types of yarn will be readily apparent from the above discussionor can be readily determined by routine tests.

The temperature of plate 34 is not critical and indeed it the yarnspeeds are slow enough, for example below about 25 to 50 yards perminute, the yarn will cool sutficiently to give good results even thoughplate 34 is eliminated and the yarn is allowed to cool by open contactwith the atmosphere. With very high yarn speeds, however, it is possiblethat the yarn ends may reach the point 39 while still at a temperaturesufiiciently high to result in loss of some of the tendency to twistpreviously imparted and for this reason the plate 34 should be employedwith such yarn speeds and retained at a temperature to result in theyarn being cooled, before it reaches the point 39, below a point atwhich it loses its tendency to twist. By the use of a cooling plate anda very eifective heating means, linear yarn speeds up to 500 yards perminute, or even higher, can be achieved. For nylon yarns the temperatureat which the yarn will retain, to a large extent, its tendency to twistis in the vicinity of 160 F. so that the plate 34 should be designed toinsure that the yarn will be below this temperature by the time itreaches point 39. A corresponding temperature for other types of yarnwill be readily apparent to those skilled in the art or can bedetermined by routine tests.

The elasticity or activity of yarns prepared according to this inventioncan be materially increased by subjecting the same to a heat treatmentwhile they are under such a low tension that they are free to contract.This operation can, if desired, be postponed until after Weaving orknitting, and it is generally more convenient to heat treat the yarn infabric form.

Having thus described my invention, what I desire to claim and secure byLetters Patent is:

1. An apparatus for processing yarn comprising in combination aplurality of yarn supply means to supply separated ends of yarn, aplurality of yarn takeup means for collecting separated ends of yarn atsubstantially equal rates, whereby when yarn ends from said supply meansare plied together a plurality of turns, separated and thereaftercollected by said takeup means, a false twist is inserted into each ofsaid yarns, and yarn heating means to heat each of said yarn ends in anarea where they are in an individually twisted condition and spatiallyseparated trom each other. 4

2. Apparatus for processing yarn comprising in combination a pair ofyarn supply means to supply two separated ends of yarn, a pair of yarntakeup means for collecting two separated ends'of yarn at substantiallyequal rates, means for placing said yarns under approximately equaltension prior to their being collected by said takeup means, wherebywhen two yarn ends are passed from said supply means to the tensioningmeans, twisted a plurality of turns about each other and are thereaftercollected by said takeup means, a false twist is inserted into each ofsaid yarns, and yarn heating means to heat the twisted yarn ends betweensaid tensioning means and the point at which said yarn ends operativelycome into contact with each other.

3. Apparatus according to claim 2 wherein said tensioning meanscomprises a driven feed roll for delivering an equal length of said twoyarns to said takeup means.

4. Apparatus according to claim 2 including means to cool said yarns atthe point where they are in mutual contact.

5. Apparatus for simultaneously processing two running lengths of yarncomprising in combination means to supply two yarn ends and to transportthe same under tension over linear paths at substantially equal linearvelocities, first and second pairs of separated yarn guide meanspositioned within the paths of said yarn ends, and yarn heating meansfor heating said two yarn ends while they are spatially separated, saidheating means being positioned between said first pair of yarn guidemeans and a point equidistant from said two pairs of yarn guide means,whereby the two yarn ends, when passing from said first pair of yarnguide means, wrapping several turns about each other and thereafterseparating to pass to said second pair of yarn guide means, act uponeach other to result in the yarn ends being twisted between the point ofmutual contact and said first pair of yarn guide means, and said twistis heat-set by said yarn heating means.

6. Apparatus for simultaneously processing two running lengths of yarncomprising in combination means to supply two yarn ends and to transportthe same under tension along linear paths at substantially equal linearvelocities, first guide means positioned in the yarn paths of said yarnends to maintain said yarn ends separated one from the other at a firstpoint in their line of travel, second guide means, spaced from saidfirst guide means, to maintain said yarn ends separated one from theother at a second point in their line of travel, whereby when said endsare twisted a plurality of turns about each other between said first andsecond points, the yarn ends act upon each other to insert false twist,and heating means positioned in the paths of said yarn ends between saidfirst guide means and the point where the yarn ends are operatively inmutual contact.

7. A method for simultaneously imparting a tendency to curl, kink andloop to a pair of thermoplastic yarn ends being transported throughlinear paths at substantially equal velocities which method comprisesseparating said yarn ends at a first and at a second point in their lineof travel, passing said ends a plurality of turns about each other in anarea intermediate said first and second points, retaining said yarn endsunder approximately equal tensions between said first and second points,whereby the yarn ends acting upon each other in said area of mutualcontact causes a false twist to be inserted into each of said yarn ends,heating said yarn ends in the portions of their respective yarn pathsimmediately preceding the area of mutual contact and while they are in atwisted condition, and subjecting said yarn ends to cooling conditionsto cool the same below a heat-setting temperature 7 at the point wheretheir mutual contact with each other is rmi ated- 8- A 1, e hod a crding to claim 7 wherein sa yarns are twisted together for ,from about10 to 25 turns.

9. A method according to claim 8 wherein said there moplastic yarns arenylon, said yarns are retained under equal tensions of approximately 0.2to 1.0 gm. per denier, the twisted yarns are heated to a temperature ofat least about 240 F. preceding the point at which they are in mutualcontact, and said yarns are cooled to a temperature of not more thanabout 160 F. before their mutual Contact is terminated.

10. A method according to claim 7 wherein said yarn ends are positivelyfed into said portions of their respective yarn paths where they areheated, at a linear rate in excess of that at which they are withdrawnfrom said portions of their yarn paths to thereby permit the yarns tocontract'upon being heated.

11. Apparatus for simultaneously processing two running ends of yarncomprising in combination means to supply two ends of yarn, first guidemeans to retain said two ends of yarn in spaced relationship withrespectto each other, second guide means to retain said ends of yarn inspaced relationship with respect to each other, a. contact yarn heater,to heat said two yarn ends by conduction, disposed in intermediate yarnflow relationship with respect to said first and second guide means, thepositional relationship of said contact yarn heater and said guide meansbeing such that said two ends of yarns can be passed a plurality ofturns about each other between said first and second guide means so thateach of said ends is individually false twisted and said contact yarnheater heats said two yarn ends only in an area where they are spatiallyseparated from each other, and the twist is heat-set thereinby passageof said two ends of yarn into effective heating relationship with saidcontact Cit yarn heater, yarn advancing means, disposed in intermediateyarn flow relationship with respect to said supply means and saidfirstguide means, to positively advance ea h f s id en of Ya n at an equal ans stant y constant first linear rate, means disposed in subsequent yarnflow relationship with respect to said second guide means to positivelyadvance each of said ends of yarn at an equal and substantially constantsecond linear rate which is less than said first linear rate, wherebythe tension in each of said ends of yarn between said first and secondguide means is determined primarily by the thermal contractioncharacteristics of said yarns.

12. Apparatus according to claim 11 including yarn cooling means to coolsaid two yarn ends in an area between said two guide means where saidtwo yarnends are in mutual contact.

13. Apparatus according to claim 11 wherein said means to advance saidyarn ends at a second selected linear rate comprises a pair of constantlinear rate yarn collecting means.

References Cited in the file of this patent UNITED STATES PATENTS2,76l,272 Vandamme Sept. 4, 1956 2,890,568 Willens June 16, 19-59FOREIGN PATENTS 1,072,786 France Mar. 17, 1954 1,076,599 France Apr. 21,1954 1,120,046 France Apr. 9, 19-56 OTHER REFERENCES Moncrieff:Artificial Fibers, copyright 1954, page '270, John Wiley and Sons, Inc,New York. (Copy in Division 21.)

